Colloidal Processing of Mn 3 O 4 -Carbon Nanotube Nanocomposite Electrodes for Supercapacitors.

This investigation addresses the challenges in the development of efficient nanostructured Mn 3 O 4 cathodes for supercapacitors. A high areal capacitance and the ability to avoid a time-consuming activation procedure for electrodes with high active mass loading of 40 mg cm -2 are reported. This facilitates practical applications of Mn 3 O 4 based electrodes. The highest capacitance of 6.11 F cm -2 (153 F g -1 ) is obtained from cyclic voltammetry at a scan rate of 2 mV s -1 and 6.07 F cm -2 (151.9 F g -1 ) from the chronopotentiometry at a current density of 3 mA cm -2 in a potential window of 0.9 V in a neutral Na 2 SO 4 electrolyte. The new approach is based on the application of rhamnolipids (RL) as a capping agent for the synthesis of Mn 3 O 4 particles and a co-dispersant for Mn 3 O 4 and carbon nanotubes, which are used as conductive additives. The size and shape of the Mn 3 O 4 particles are influenced by RL. The enhanced performance of the electrodes is linked to the chemical structure and properties of RL molecules, which exert influence on Mn 3 O 4 particle size and shape during synthesis, reduce agglomeration, facilitate RL adsorption on Mn 3 O 4 and carbon nanotubes, and influence their co-dispersion and mixing at the nanometric scale.